1
2sinx/2cosx/2+cos²x/2-sin²x/2+sin²x/2+cos²x/2=0
2sinx/2cosx/2+2cos²x/2=0
2cosx/2*(sinx/2+cosx/2)=0
cosx/2=0⇒x/2=π/2+πk⇒x=π+2πk,k∈z
sinx/2+cosx/2=0/cosx/2
tgx/2+1=0⇒tgx/2=-1⇒x/2=-π/4+πk⇒x=-π/2+2πk,k∈z
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2
2cos²2x-1-(cos2x+1)/2-1=0/*2
4cos²2x-2-cos2x-1-2=0
4cos²2x-cos2x-5=0
cos2x=a
4a²-a-5=0
D=1+80=81
a1=(1-9)/8=-1⇒cos2x=-1⇒2x=π+2πk⇒x=π/2+πk,k∈z
a2=(1+9)/8=1,25⇒cos2x=1,25>1 нет решения